We had a number of posters report on the baptism rate at conventions which is usually less than 1% and rates lower than 0.5% is by no means uncommon. Despite this there is still a positive growth rate in the US (0.71% according to the yearbook) and I wonder how these numbers relate. I hope someone can help me out if these assumptions appear sound:
Lets suppose in an area of the US there is a baptism rate of r (rate observed) for instance r=0.5% would correspond to 7400 in attendance and 37 baptized because:
r = N(Baptisms at convention) / N(Attendance at convention) = 37 / 7400
We need to relate this quantity to the actual rate of baptisms (yearbook growth rate). There are three principal unknowns:
- q : Fraction of total baptisms which takes place at conventions
- Pa : Chance an average JW "publisher" will attend (and be counted in) the total number of attendants at the convention
- Pb : Chance a random person at the convention is also a JW publisher
q is required because not all baptisms take place at conventions. If q=1 we assume all baptisms take place at conventions and if q=0.5 we assume half of all baptisms take place at conventions.
Pa is the chance a JW publisher will be (counted in) the total number of attendants at the conventions. For instance, if all JWs attend two conventions then Pa=2 and if an average JW attend half of the conventions then Pa = 0.5. This number is lowered by infirm JWs, ill JWs, JWs who are out of the seats getting icecream etc.
Pb is the chance a person who is at the convention is also an "average" publisher (presumably, outsiders, children and DF/DA'd are also counted as attendants at conventions but these are not publishers)
Lets give an illustration: Suppose q=0.75 (75% of all baptisms take place at conventions) and Pa=0.9 (A JW will on average miss out one of 10 conventions when double-attendance is included) and Pb = 0.9 (90% of attendants at conventions are publishers and not faded, DF'd, children, any of you guys, etc.). Then we can compute the total (effective) growth rate as:
G = r * Pa / (q * Pb) = r * 1.33
We need to substract from this number the rate with which JWs leave. First there is death. The death rate in the US is about 0.8%, however we must factor in that we are interested in the rate with which average publishers die (small children who rarely die are not publishers). If we suppose JWs become "average publishers" at age 10 (on average), this would boost the death rate by a little more than 10% (rough guesstimate). In addition many JWs presumably become inactive (due to age) a few years before they die but let's not count that. For simplicity, let's put the death rate at 0.9% (we should also factor in the JW population may be younger/older than the average person or live more/less healthy lives etc.).
Secondly there is the rate with which people leave (DF/DA/fade) and never return. Let's suppose 1 out of 100 leave (i.e. stops being a regular publisher) every year for reasons other than death and half of these never return, that puts the "leave" rate at 0.5%. In total we get the effective growth rate to be:
G(effective) = r * Pa / (q * Pb) - (%Dies) - (%Leaves) = r * 1.33 - 1.4
Thus with these numbers the baptism rate at conventions should be a little more than 1% to maintain equilibrium and about 1.6% to account for the current JW growth rate of 0.71 in the yearbooks (1.6 * 1.33 - 1.44 = 0.71).
Thus, if the baptism rates of 0.5% are representative something fishy is going on with these assumptions... There are a few options:
- I am missing something (the "average publisher" may differ from "the average person" in a significant way)
- The numbers are wrong (q, Pa, Pb, the "leave-rate" or "death-rate"). For instance there could be more DF/Inactives at the convention (Pb is lower than 0.9%). I am probably the worst person to guess these numbers so I hope someone else will give his or her view.
- A few conventions may account for most of the growth whereas the "typical" convention signifies a decline ("the amazing hispanish conventions")
- Ex-JWs who attend conventions with high growth rate don't bother to report the high growth rate here or on reddit because it is discouraging
To translate the baptism rate reported from conventions into yearbook growth rate we must make several assumptions. It would be interesting to narrow down plausible values for these assumptions to better estimate local growth of the JWs.